Applicants claim the priority of Japanese patent application, Ser. No, 11-178911, filed Jun. 24, 1999.
The present invention relates to a carburetor for an engine and, more particularly, to a throttle valve lever capable of controlling the rate of fuel flow in a rotary throttle valve type carburetor.
For a throttle valve lever capable of controlling the rate of fuel flow in a rotary throttle valve type carburetor, a problem concerning the structural integrity of the lever often arises as the lever is utilized over time. For example, a carburetor of a rotary throttle valve type is disclosed in JP Patent Application Number 9-215679 and has a throttle valve and a throttle valve lever molded of synthetic resin. Although the sliding portions of such a carburetor exhibit excellent operational smoothness, the carburetor has the distinct drawback of being unable to reliably control the amount of fuel and the rate of fuel flow therethrough. In particular, when excessive force is exerted upon the throttle valve lever of the carburetor over time, such force often eventually causes structural deformation of the throttle valve lever and/or structural looseness and rattle at the joint between the throttle valve lever and the shaft portion of the throttle valve. As a result, undesired variation in the amount of fuel and the rate of fuel flow for engine operation typically occurs as the throttle valve lever and throttle valve are subsequently manipulated and moved into their many operative positions. In light of such, the prospect of utilizing such a carburetor often produces fear and concern among manufacturers that strict exhaust gas regulations cannot be properly observed and conformed to if such a carburetor is incorporated within a particular engine design.
In view of the above, there is a present need in the art for a throttle valve lever or a throttle valve lever assembly which maintains its structural integrity when utilized over time. More particularly, there is a present need in the art for a throttle valve lever or a throttle valve lever assembly which is resistant to both structural deformation of the throttle valve lever and looseness and rattle at the joint between the throttle valve lever and the shaft portion of the throttle valve when utilized over time.
The present invention provides a throttle valve lever for controlling the rate of fuel flow in a rotary throttle valve type carburetor. The throttle valve lever has increased stiffness to help prevent structural deformation due to excessive force exerted and applied to the lever over time. According to the present invention, the throttle valve lever basically includes an oblong structure comprising synthetic resin and an oblong reinforcement plate comprising metal. The resin structure has a hole defined therethrough, which is capable of fitting around the shaft of a throttle valve of a carburetor, and also has a lever portion at one end of the resin structure. Similarly, the metal plate has a hole defined therethrough, which is capable of fitting around the shaft of a throttle valve of a carburetor, and also has a lever portion at one end of the metal plate. The metal plate is embedded within the resin structure such that the lever portion of the resin structure and the lever portion of the metal plate are correspondingly situated, the hole of the resin structure and the hole of the metal plate are aligned, and the metal plate is exposed at the metal plate hole and is capable of direct and fitted contact with the throttle valve shaft.
The incorporation of the metal plate within the lever serves to increase the overall stiffness of the lever and thereby helps fortify the structural integrity of the lever and prevent structural deformation. Furthermore, exposure of the metal plate at the metal plate hole enables the lever to be mounted on the shaft of a throttle valve at the metal plate hole such that the metal plate itself is in direct and fitted contact with the throttle valve shaft. In this way, the structural integrity of a throttle valve lever assembly is also fortified such that looseness and rattle at a joint between the throttle valve lever and the shaft of the throttle valve is thereby largely prevented.
In a preferred embodiment of the throttle valve lever, the metal plate is embedded within the resin structure by insert molding. The metal plate also preferably has a plurality of throughholes which are defined through the metal plate. The throughholes enable the metal plate to be embedded within the resin structure such that the resin structure covers and fills the metal plate throughholes to thereby enhance the overall structural integrity of the throttle valve lever.
Also in a preferred embodiment of the throttle valve lever, the hole in the metal plate is smaller than the hole in the resin structure. The metal plate hole preferably defines a first surface and a second surface within the metal plate such that both the first surface and the second surface are substantially flat. The first surface and the second surface of the metal plate hole preferably have different lengths and are situated substantially parallel with each other. In this way, the shaft of a throttle valve can be precisely fitted into the metal plate hole in only one particular orientation. As a result, improper mounting of the throttle valve lever onto the shaft of the throttle valve as well as looseness and rattle at the joint between the throttle valve lever and the throttle valve shaft are thereby prevented.
Further in a preferred embodiment of the throttle valve lever, the resin structure, in addition to having a lever portion at one end, also has a cam portion at another end of the resin structure which is remote from the lever portion of the resin structure. Similarly, the metal plate, in addition to having a lever portion at one end, also preferably has a cam portion at another end of the metal plate which is remote from the lever portion of the metal plate. The metal plate is preferably embedded within the resin structure such that the resin structure cam portion and the metal plate cam portion are correspondingly situated and such that the resin structure cam portion and the metal plate cam portion cooperatively define an engageable cam surface. The cam surface preferably defines a groove of graduated depth which extends arcuately along the perimeters of the resin structure cam portion and the metal plate cam portion on the underside of the throttle valve lever. In one particular preferred embodiment, the metal plate is covered by the resin structure within the groove such that the resin structure is directly engageable by a cam follower within the groove. In another particular preferred embodiment, the metal plate is exposed within the groove such that the metal plate is directly engageable by a cam follower within the groove. Such a cam surface and groove are, for example, suitable for a cold-start fuel increasing mechanism for an engine.
Lastly in a preferred embodiment of the throttle valve lever, the resin structure also has a swivel throughhole defined through the resin structure lever portion, and the metal plate also has a swivel throughhole defined through the metal plate lever portion. The metal plate is preferably embedded within the resin structure such that the swivel throughhole of the resin structure and the swivel throughhole of the metal plate are aligned with each other and engageable with a swivel. Preferably, the swivel throughhole of the resin structure is smaller than the swivel throughhole of the metal plate.
In addition to a throttle valve lever, the present invention also provides a throttle valve lever assembly. According to the present invention, the throttle valve lever assembly basically includes a rotary throttle valve with a shaft portion, an oblong structure comprising synthetic resin, and an oblong reinforcement plate comprising metal. The resin structure has a hole defined therethrough, within which the shaft portion of the throttle valve is fitted, and also has a lever portion at one end of the resin structure. Similarly, the metal plate has a hole defined therethrough, within which the shaft portion of the throttle valve is fitted, and also has a lever portion at one end of the metal plate. The metal plate is embedded within the resin structure such that the lever portion of the resin structure and the lever portion of the metal plate are correspondingly situated, the hole of the resin structure and the hole of the metal plate are aligned, and the metal plate is in direct and fitted contact with the throttle valve shaft portion.
As in the case of the above-mentioned throttle valve lever, the incorporation of the metal plate within the throttle valve lever assembly serves to increase the overall stiffness of the assembly and thereby helps fortify the structural integrity of the assembly and prevent structural deformation. Furthermore, since the metal plate is in direct and fitted contact with the throttle valve shaft portion at the metal plate hole, the structural integrity of the throttle valve lever assembly is further fortified because looseness and rattle at the joint between the throttle valve lever and the shaft of the throttle valve are thereby largely prevented.
In a preferred embodiment of the throttle valve lever assembly, the hole in the metal plate is smaller than the hole in the resin structure. The throttle valve has an axial throughhole through the length of the throttle valve such that the shaft portion of the throttle valve has a hollow tip end. Preferably, the hollow tip end is fitted through the metal plate hole, bent radially outward, and tightly crimped onto the metal plate. In this way, looseness and rattle at the joint between the throttle valve lever and the shaft of the throttle valve are thereby largely prevented. Furthermore, the hole in the metal plate preferably defines a first surface and a second surface within the metal plate such that both the first surface and the second surface are substantially flat. The first surface and the second surface of the metal plate hole preferably have different lengths and are situated substantially parallel with each other. The hollow tip end of the throttle valve shaft portion preferably has a cross-section which corresponds to the shape of the metal plate hole so that the hollow tip end precisely fits the metal plate hole in only one particular orientation. As a result, improper mounting of the throttle valve lever onto the shaft of the throttle valve as well as looseness and rattle at the joint between the throttle valve lever and the throttle valve shaft are thereby prevented.
Objects, features, and advantages of the present invention include providing a throttle valve lever and throttle valve lever assembly which are resistant to structural deformation, resistant to loosening and rattling, and which are compact, rugged, durable, of relatively simple design and economical manufacture and assembly, and which in service have a long useful life.